Sunday, June 14, 2009

Hide Glue

For those of you who don't know, instruments in the violin family (violins or fiddles, violas, basses, and cellos) are put together with hide glue. This is glue made from the hide of an animal, such as a rabbit, goat, horse or cow. This glue can be found in two different formats -- crystals (for melting) or ready-to-use in a bottle. The ready-to-use version has additional ingredients that keep it in a liquid form, but which also make it unsuitable for most instrument repair usages due to the weaker bond which is caused by these additional ingredients. (It can be used for the nut, but that's about it.) The crystal form is put into a special pot along with some water, and then is heated until it melts. Once the right consistancy between crystals and water is met and the glue is completely melted, it is ready for use. Generally, only the amount of glue needed for the repair is used, as the unused portion of glue can become moldy fairly quickly.

Hide glue is made to come apart. There's a very good reason why it is used instead of more permanent glues. It has excellent adhesive properties and a strong bond as long as it doesn't get wet or hot. When a fiddle (or other instrument in the violin family) develops a crack or has an accident, the instrument will most likely need to be taken apart to repair the crack properly. If it has been glued by Uncle Henry so that "it will never come apart again!", the wood of the instrument can be damaged in just getting the instrument apart. When hide glue is used, it can be heated and the instrument can be taken apart without damage to the instrument itself.

Cracks are not simply glued. They are also cleated from the inside to keep the crack from further separating or from growing. Many times, cracks that just appear with age are due to wood shrinkage. Most commonly, the top is made from spruce, and the sides (ribs) are made from maple. These woods shrink at different rates, even if they have been aged before the instrument is made. The ribs tend to pull outward from the top, so over time, cracks may develop in the top even if instrument has been well-cared for. When releasing or removing the top for crack repair, this tension is released so that the crack doesn't continue to have pressure on it. Just glueing the crack without cleating or releasing this tension may cause the crack to reappear or worsen.

Now, why is all of this important to know? There are several reasons. For one, that instrument that someone finds in their attic all in pieces should not be thrown away. It could be valuable even though it isn't playable! The hide glue got hot in the attic and the parts all separated. Not a big deal to a luthier (specialized instrument repair person), though it can be pricy to put something like this back together again! A luthier should be able to give you an estimate on the cost, and should also be able to tell you whether it's worth your money to do this, or whether you would be better off selling or giving the parts away. Be sure to take the instrument to someone who knows something before simply throwing it away. Even an instrument that is not valuable might have parts that could be reused on another instrument. Someone, somewhere, will be able to use these parts. Just about any luthier would gladly receive these parts from you!

One very important reason for knowing this information is so that you can take proper care of your instrument. While some instruments can take more heat and humidity than others, even though it's not good for ANY instrument to get too hot or wet, an instrument in the violin family cannot take much. With 300 pounds of pressure on a bridge or top of a tuned violin, a little heat goes a long ways! If your instrument gets too hot or wet, it will come apart!!!! A good rule of thumb is to keep your instrument only in places that a "normal" person would be comfortable. You would not want to be in a hot trunk...

One final reason for knowing this information is so that you don't try to make repairs to your instrument yourself. There are some very handy and detailed oriented persons out there who would probably be very good at instrument repair with a little bit of instruction. If you want to try, I certainly won't stop you. HOWEVER, please don't use regular glue...or gorilla glue...or super glue...or wood glue...

No comments: